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Measurement of the Kerr Spin Parameter by Observation of a Compact Object's Shadow

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arxiv 0904.3575 v3 pith:ZBED45TO submitted 2009-04-23 astro-ph.HE gr-qc

classification astro-ph.HEgr-qc
keywords parameterkerrshadowspinangleapparentblackhole
verification ladder T0 review T1 audit T2 compute T3 formal

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A black hole casts a shadow as an optical appearance because of its strong gravitational field. We study how to determine the spin parameter and the inclination angle by observing the apparent shape of the shadow, which is distorted mainly by those two parameters. Defining some observables characterizing the apparent shape (its radius and distortion parameter), we find that the spin parameter and inclination angle of a Kerr black hole can be determined by the observation. This technique is also extended to the case of a Kerr naked singularity.

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Cited by 16 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Determining Kerr black hole spin and inclination from a segment of the critical curve in black hole images

    gr-qc 2026-06 unverdicted novelty 7.0 of 10

    Three observables on a standardized segment of the Kerr critical curve uniquely fix spin a/M, inclination i, and segment location r_nl within the considered domain.

  2. Constitutive birefringence and critical curves in the rotating Garc\'ia--D\'iaz black hole

    gr-qc 2026-06 unverdicted novelty 7.0 of 10

    In the rotating García-Díaz NLED black hole the Fresnel quartic factorizes into two optical metrics whose critical families project to distinct contours Γ+ and Γ- whose angular separation is generated by the constitut...

  3. Strong-deflection expansion of the deflection angle near a degenerate photon sphere

    gr-qc 2026-03 unverdicted novelty 7.0 of 10

    Derives a factorized leading term for the strong deflection angle near degenerate photon spheres using local expansion of the effective potential and Weyl tensor measures.

  4. Rotating Black Holes with Primary Scalar Hair: Shadow Signatures in Beyond Horndeski Gravity

    gr-qc 2026-02 unverdicted novelty 7.0 of 10

    Rotating black holes with primary scalar hair in beyond Horndeski gravity produce shadows whose diameter increases for negative Q and whose distortion increases for positive Q, with EHT bounds on M87* restricting but ...

  5. Topological charge and black hole photon spheres in massive gravity

    gr-qc 2025-09 unverdicted novelty 7.0 of 10

    In dRGT massive gravity, static spherically symmetric black holes exhibit zero, one, or two photon spheres whose topological charges and stability patterns differ from Einstein gravity and from horizonless compact objects.

  6. Dark matter environments and safeguards for spacetime inference from horizon scale interferometry

    gr-qc 2026-07 conditional novelty 6.0 of 10

    Using public 2017 M87* closure data, a frozen Kerr source fails an absolute adequacy test and the differential tidal-charge response fails numerical convergence, so no posterior or bound is reported.

  7. A Universal Framework for Horizon-Scale Tests of Gravity with Black Hole Shadows

    gr-qc 2025-11 conditional novelty 6.0 of 10

    An adaptive ray-tracing and MCMC framework estimates shadow observables for arbitrary stationary metrics; applied to the Kerr–Bertotti–Robinson spacetime it yields an Sgr A* horizon-scale magnetic field of about 93 G ...

  8. Optical Characteristics of the Kerr-Bertotti-Robinson Black Hole

    gr-qc 2025-08 conditional novelty 6.0 of 10

    For the Kerr-Bertotti-Robinson black hole, the magnetic field mainly enlarges the shadow and Einstein ring while rotation mainly distorts the shadow shape, and current M87* and Sgr A* data give only weak bounds on the field.

  9. Influence of Observer Inclination and Spacetime Structure on Photon Ring Observables

    gr-qc 2024-11 conditional novelty 6.0 of 10

    For Johannsen-Psaltis spacetimes, the polar photon-ring time delay depends only on spin and shadow size, while the azimuthal shift probes the metric ratio F/N, enabling future spin and frame-dragging tests.

  10. Determining parameters of Kerr-Newman black holes by shadow observation from finite distance and spatial infinity

    gr-qc 2024-11 conditional novelty 6.0 of 10

    The shadow contour of a Kerr-Newman black hole observed at infinity uniquely fixes (a/M, Q/M, i), while finite-distance shadows are degenerate for zero spin.

  11. Influence of Perfect Fluid Dark Matter on Shadow Observables of Yang-Mills modified charged black holes

    gr-qc 2025-09 reject novelty 4.0 of 10

    A rotating Yang-Mills charged black hole surrounded by perfect fluid dark matter is shown to have a smaller and more distorted shadow as the dark matter parameter increases, with EHT-derived bounds on the dark matter ...

  12. Thermodynamics and Shadows of Kerr black holes endowed with a global monopole charge

    gr-qc 2025-06 reject novelty 4.0 of 10

    The authors derive shadow and thermodynamic quantities for a Kerr-like metric with a global monopole term in Δ, and claim EHT observations constrain the monopole charge α.

  13. Shadows and accretion disk images of charged rotating black hole in modified gravity theory

    gr-qc 2024-11 conditional novelty 4.0 of 10

    Ray-traced images of the Kerr-Newman-MOG black hole show that the MOG parameter α enlarges and rounds the shadow, and its effect beats that of the electric charge Q.

  14. Shadows of rotating black holes in effective quantum gravity

    gr-qc 2024-11 conditional novelty 4.0 of 10

    For two covariant effective quantum gravity black holes, the quantum parameter ζ shrinks the shadow at moderate spin and creates a cuspy shadow edge near extremality.

  15. Effect of gravitational wave on shadow of a Schwarzschild black hole

    gr-qc 2019-08 conditional novelty 4.0 of 10

    Numerical ray tracing shows that a first-order gravitational perturbation makes a Schwarzschild black hole shadow oscillate, stretch, and develop self-similar fractal boundary structures over time.

  16. Deflection Angle of Regular Black Holes in Nonlinear Electrodynamics: Gauss-Bonnet Theorem, Time Delay, Shadow, and Greybody Bound

    gr-qc 2025-09 conditional novelty 3.0 of 10

    For a singularity-free charged black hole from nonlinear electrodynamics, this paper computes weak-field deflection angles (vacuum and plasma), time delay, shadow radius, and greybody bounds, finding charge reduces an...

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